I, am, at Lucre Island, in the Palce of Prostheses. I, am, in the shop talking to Dave and asked he about a hand. I use the music box and I try to steal the hand, but I can't seem to do this. I have already picked up the file, what am, I doing wrong? How do you get the prosthese hand?

If the problem is just in getting the game to highlight "Look at wooden prosthetic hand" the solution is to use the PageDown key to scroll along the choices of actions. This is the one point in the game where it seems you have to do this rather than just move Guybrush to the right spot.